Semiconductor apparatus having a semicondutor element with a high dielectric constant film

ABSTRACT

A semiconductor apparatus wherein a device formed on a semiconductor substrate comprises a gate insulating film including a high dielectric constant film formed on the substrate and an anti-reaction film formed on the high dielectric constant film, and a gate electrode formed on the anti-reaction film, the high dielectric constant film comprises a film containing at least one of Hf and Zr, and Si and O, or a film containing at least one of Hf and Zr, and Si, O and N, the anti-reaction film comprises an SiO 2  film, a film containing SiO 2  as a main component and at least one of Hf and Zr, a film containing SiO 2  as a main component and N, a film containing SiO 2  as a main component, Hf and N, a film containing SiO 2  as a main component, Zr and N, or a film containing SiO 2  as a main component, Hf, Zr and N.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/927,115,filed Aug. 27, 2004 now U.S. Pat. No. 7,265,427, and is based upon andclaims the benefit of priority from prior Japanese Patent ApplicationNo. 2003-305779, filed Aug. 29, 2003, the entire contents of both ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor apparatus, and inparticular, to a semiconductor apparatus in which a transistor using ahigh dielectric constant film whose dielectric constant is greater thanthat of a conventional gate insulating film for a gate structure isformed in a semiconductor substrate, and a method of manufacturing thesemiconductor apparatus.

2. Description of the Related Art

In recent years, elements have become minute due to the high-integrationand increase in speed of semiconductor apparatuses such as a large-scaleintegration (LSI). Accompanying these, in a MOS structure which is acomponent of a function device such as a capacitor or a transistor, ithas been required that an SiO₂ gate insulating film is further madethinner. However, when a film thickness of a silicon oxide film is lessthan or equal to 3 nm, because electrons come to bring about directtunneling in an electric field region where the device operates, theproblem that a leakage current is increased and an electric powerconsumption of the device is increased is brought about. Therefore, anext-generation gate insulating film which can be replaced with thesilicon oxide film has been required. Then, recently, a high dielectricconstant film whose relative dielectric constant is higher than that ofthe silicon oxide film has been paid attention. The reason for this isthat the high dielectric constant film with a film thickness thickerthan that of the silicon oxide film can obtain the same capacitance asthat of the silicon oxide film. Due to the film thickness of aninsulating film being made thicker, it is possible to reduce aprobability in which electrons tunnel through the insulating film, i.e.,it is possible to suppress the generation of a tunnel current.

Then, as a high dielectric constant gate insulating film replaced withan SiO₂ film, for example, a hafnium silicate (Hf-silicate) film or thelike is cited as a candidate. Further, a generally used manufacturingmethod such as a chemical vapor deposition (CVD) method is preferablyused at the time of manufacturing a large-scale integration (LSI).

When a manufacturing method which has been generally used is used, it isnecessary to use a general silicon as a gate electrode. However, when asilicon gate is used, a fixed charge is generated in the vicinity of theinterface between the silicon gate electrode and the hafnium silicategate insulating film. Accordingly, in particular, in a case of ap-channel metal oxide semiconductor (MOS) transistor, a change in athreshold value of 0.6 V or more than an ideal value arises. Therefore,there has been the problem that it is difficult to design the LSI.

As a prior art using a high dielectric constant film as a gateinsulating film, in Jpn. Pat. Appln. KOKAI Publication No. 2003-152101,there is disclosed that a high dielectric substance whose relativedielectric constant is greater than that of a silicon nitride film, forexample, a group 4A elemental oxide such as a ZrO₂ film or an HfO₂ film,a Ta₂O₅ film or the like is used as a gate insulating film. Further, inJpn. Pat. Appln. KOKAI Publication No. 2002-170825, there is disclosedthat a gate insulating film is formed by combining a siliconoxide/nitride film with a relative dielectric constant of 5 to 7 and ahigh dielectric constant film (an oxide of a metal such as Zr, Hf, La,Ti, Ta, Y or A1). Furthermore, in Jpn. Pat. Appln. KOKAI Publication No.2002-280461, there is disclosed that a gate insulating film is composedof a first insulating film which is a low dielectric constant film and asecond insulating film which is a high dielectric constant film. One ofa silicon oxide film, a silicon nitride film, and a siliconoxide/nitride film is used as the low dielectric constant film, and oneof TiO₂, ZrO₂, HfO₂, PrO₂, and the like, or a mixture of two or morethereof is used as the high dielectric constant film.

As described above, when a manufacturing method which has been generallyused is used, it is necessary to use a general silicon as a gateelectrode. However, when a silicon gate is used, a fixed charge isgenerated in the vicinity of the interface between the silicon gateelectrode and the hafnium silicate gate insulating film. Accordingly, inparticular, in a case of a p-channel metal oxide semiconductor (MOS)transistor, a change in a threshold value of 0.6 V or more than an idealvalue arises. Therefore, there has been the problem that it is difficultto design the LSI.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided asemiconductor apparatus comprising:

a semiconductor substrate; and

a function device formed on the semiconductor substrate,

wherein the function device comprises a gate structure including a gateinsulating film which is formed of a high dielectric constant filmformed on the semiconductor substrate, an anti-reaction film formed onthe high dielectric constant film, and a gate electrode formed on theanti-reaction film,

the high dielectric constant film comprises a film made of a materialcontaining at least one of Hf and Zr, and Si and O, or a film made of amaterial containing at least one of Hf and Zr, and Si, O and N,

the anti-reaction film comprises an SiO₂ film, a film made of a materialcontaining SiO₂ as a main component and at least one of Hf and Zr, afilm made of a material containing SiO₂ as a main component and N, afilm made of a material containing SiO₂ as a main component, Hf and N, afilm made of a material containing SiO₂ as a main component, Zr and N,or a film made of a material containing SiO₂ as a main component, Hf, Zrand N, in which when the anti-reaction film contains one of Hf and Zr, acomposition ratio of Hf or Zr is less than 1 atom %, when theanti-reaction film contains Hf and Zr, a total composition ratio of Hfand Zr is less than 1 atom %, and when the anti-reaction film containsN, a composition ratio of N is less than 20 atom %.

According to another aspect of the present invention, there is provideda method of manufacturing a semiconductor apparatus comprising:

forming a high dielectric constant film on a semiconductor substrate,the high dielectric constant film comprising a film made of a materialcontaining at least one of Hf and Zr, and Si and O, or a film made of amaterial containing at least one of Hf and Zr, and Si, O and N,

forming on the high dielectric constant film an anti-reaction filmforming a gate insulation film together with the high dielectricconstant film, the anti-reaction film comprising an SiO₂ film, a filmmade of a material containing SiO₂ as a main component and at least oneof Hf and Zr, a film made of a material containing SiO₂ as a maincomponent and N, a film made of a material containing SiO₂ as a maincomponent, Hf and N, a film made of a material containing SiO₂ as a maincomponent, Zr and N, or a film made of a material containing SiO₂ as amain component, Hf, Zr and N, in which when the anti-reaction filmcontains one of Hf and Zr, a composition ratio of Hf or Zr is less than1 atom %, when the anti-reaction film contains Hf and Zr, a totalcomposition ratio of Hf and Zr is less than 1 atom %, and when theanti-reaction film contains N, a composition ratio of N is less than 20atom %, and

forming a gate electrode on the anti-reaction film, the gate electrodeforming a gate structure together with the gate insulating film.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a sectional view of a MOS structure according to a firstembodiment of the present invention.

FIG. 2 is a characteristic diagram showing the dependence of a flat bandvoltage on a gate insulating film thickness.

FIG. 3 is a characteristic diagram showing the dependence of a flat bandvoltage on a gate insulating film thickness.

FIG. 4 is a sectional view of a MOS structure capacitor according to asecond embodiment of the present invention.

FIG. 5 is a sectional view of a semiconductor structure, for explaininga step of manufacturing a MOS transistor according to a third embodimentof the present invention.

FIG. 6 is a sectional view of a semiconductor structure, for explaininga step of manufacturing the MOS transistor according to the thirdembodiment of the present invention.

FIG. 7 is a sectional view of a semiconductor structure, for explaininga step of manufacturing the MOS transistor according to the thirdembodiment of the present invention.

FIG. 8 is a sectional view of a semiconductor structure, for explaininga step of manufacturing the MOS transistor according to the thirdembodiment of the present invention.

FIG. 9 is a sectional view of a semiconductor structure, for explaininga step of manufacturing the MOS transistor according to the thirdembodiment of the present invention.

FIG. 10 is a sectional view of a semiconductor structure, for explaininga step of manufacturing the MOS transistor according to the thirdembodiment of the present invention.

FIG. 11 is a sectional view of a semiconductor structure, for explaininga step of manufacturing the MOS transistor according to the thirdembodiment of the present invention.

FIG. 12 is a circuit diagram of a CMOS transistor.

FIG. 13 is a sectional view of a semiconductor structure, for explaininga step of manufacturing a MOS transistor according to a fourthembodiment of the present invention.

FIG. 14 is a sectional view of a semiconductor structure, for explaininga step of manufacturing the MOS transistor according to the fourthembodiment of the present invention.

FIG. 15 is a sectional view of a semiconductor structure, for explaininga step of manufacturing the MOS transistor according to the fourthembodiment of the present invention.

FIG. 16 is a sectional view of a semiconductor structure, for explaininga step of manufacturing the MOS transistor according to the fourthembodiment of the present invention.

FIG. 17 is a sectional view of a semiconductor structure, for explaininga step of manufacturing a MOS transistor according to a fifth embodimentof the present invention.

FIG. 18 is a sectional view of a portion of a MOS transistor accordingto a sixth embodiment of the present invention.

FIG. 19 is a diagram for explanation of a composition ratio of aninsulating film for use in the MOS transistor of the sixth embodiment ofthe invention.

FIG. 20 is a diagram for explanation of another composition ratio of theinsulating film for use in the MOS transistor of the sixth embodiment ofthe invention.

FIG. 21 is a block diagram of a NAND region and a sense amplifiercircuit of a NAND type flash memory.

FIG. 22 is a plan pattern view of a HAND type flash memory.

FIG. 23 is an equivalent circuit diagram of the NAND type flash memoryshown in FIG. 22.

FIG. 24 is a block diagram for schematically showing a DRAM mixed LSI ora SRAM mixed LSI.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings.

First Embodiment

FIG. 1 is a sectional view of a metal oxide semiconductor (MOS)structure formed on a silicon semiconductor substrate according to afirst embodiment of the present invention, and FIGS. 2 and 3 arecharacteristic diagrams showing the dependence of a flat band voltage ona gate insulating film thickness. A generally called MOS structureformed on a silicon semiconductor substrate is applied to a functiondevice such as a capacitor or a transistor. In the present embodiment,an example in which the MOS structure is applied to a transistor will bedescribed.

Source/drain regions (not shown) are formed on a surface region of asilicon semiconductor substrate 101, and a channel region 103 is formedin the silicon semiconductor substrate 101 between the source/drainregions. A high dielectric constant film 104 such as a hafnium silicate(Hf-silicate) film is formed on the channel region 103, and ananti-reaction film 105 such as an SiO₂ film is formed on the highdielectric constant film 104. The high dielectric constant film 104 andthe anti-reaction film 105 constitute a gate insulating film. Apolycrystalline silicon gate electrode 106 is formed on theanti-reaction film 105. The substrate is not limited to a siliconsemiconductor substrate, and an SOI substrate can be used.

Here, the aforementioned high dielectric constant film is(MO₂)_(x)(SiO₂)_(1-x), (where 0.01<x≦1 and M is a quadrivalent metal. AsM, Hf and Zr can be cited. Note that N (nitrogen) may be containedtherein. When N (nitrogen) is contained, a composition ratio of o(oxygen) in the above-described equation is made small.

Any of a vapor deposition method, a sputtering method, a sol-gel method,a laser ablation method, and a chemical vapor deposition (CVD) methodmay be used as a method of forming the high dielectric constant filmincluding a hafnium silicate film. For example, by using a CVD method, ahafnium silicate film formed from Hf, Si, and O can be formed bysimultaneously supplying TEOS (Si(OC₂H₅)₄) and HTB (Hf(OC(CH₃)₃)₄) andO₂ thereto at 1 Torr and 600° C. A composition ratio Hf/(Hf+Si) can bevaried by adjusting the quantity of supplying TEOS and HTB. Further, afilm thickness can be varied by adjusting the time of supplying TEOS andHTB.

Further, after a hafnium silicate film (HfSiO film) consisting of Hf,Si, and O is formed, for example, by using a CVD method, heat treatmentis carried out onto the substrate for five minutes at 100 Torr and 800°C. in an NH₃ atmosphere, whereby nitrogen N is introduced into thehafnium silicate film, and for example, it can be made to be a hafniumsilicate film (HfSiON film) in which the composition ratio of N is(N/(Hf+Si+Q+N))=about 10 to 20 atom %.

The anti-reaction film 105 is preferably formed from SiO₂. However, 20atom % or less N and 1 atom % or less Hf (metal M in a high dielectricconstant film in the broad sense) may be contained therein. It is notpreferable that N is over 20 atom %, which generates a positive fixedcharge in the anti-reaction film 105. It is not preferable that Hf isover 1 atom %, which generates a positive fixed charge between theanti-reaction film 105 and the polycrystalline silicon gate electrode106.

Further, in order to sufficiently obtain the advantage that the gateinsulating film is a high dielectric constant film, the film thicknessof the anti-reaction film 105 is preferably thinner than the filmthickness of the high dielectric constant film 104. It is morepreferable that a film thickness in which the anti-reaction film 105 isconverted into SiO₂ is thinner than a film thickness in which the highdielectric constant film 104 is converted into SiO₂. For example, when ahafnium silicate film in which a composition ratio of Hf is(Hf/(Hf+Si))=30% and the film thickness is 4 nm is used as the highdielectric constant film 104, the relative dielectric constant is about8. Therefore, as the anti-reaction film 105 formed from SiO₂ whoserelative dielectric constant is 3.9, the film thickness is preferablyless than or equal to 2 nm. Note that, when N or Hf is contained in theanti-reaction film 105, because the relative dielectric constant of SiO₂becomes high, the film thickness of the anti-reaction film 105 may bemade thicker than that in the case where N or Hf is not contained in theanti-reaction film 105.

In the present embodiment, the gate electrode 106 is to be apolycrystalline silicon gate electrode. However, the gate electrode 106may be a polycrystalline silicon gate electrode containing a dopant.Further, for example, the gate electrode 106 may be a gate electrodeusing silicon germanium (SiGe) into which B, P, As, or the like isinjected, or may be a high refractory metallic silicide gate electrodeusing tungsten suicide (WSi) or the like.

FIGS. 2 and 3 are respectively characteristic diagrams showing thedependence of a flat band voltage on a gate insulating film thickness,and the ordinate denotes a flat band voltage Vfb(V), and the abscissadenotes a film thickness(nm) of a hafnium silicate film.

The characteristics of FIGS. 2 and 3 are to plot the flat band voltageswhich had been respectively obtained, as an gate insulating film on ap-type silicon semiconductor substrate by using-polycrystalline siliconas a gate electrode, in a case where a hafnium silicate film in which acomposition ratio of Hf is Hf/(Hf+Si)=30% and the film thickness is 4 nmis formed, a case where a hafnium silicate in which a composition ratioof Hf is Hf/(Hf+Si)=30% and the film thickness is 7 nm is formed, and acase where a hafnium silicate in which a composition ratio of Hf isHf/(Hf+Si)=30% and the film thickness is 10 nm is formed. The flat bandvoltages Vfb shown in FIG. 2 are flat band voltages Vfb when B (boron)is doped in the polycrystalline silicon gate electrode, and the flatband voltages WI, shown in FIG. 3 are flat band voltages Vfb when P(phosphorus) is doped in the polycrystalline silicon gate electrode, andflat band voltages Vfb when As (arsenic) is doped in the polycrystallinesilicon gate electrode.

In FIGS. 2 and 3, flat band voltages obtained in a case where the gateinsulating film is formed from SiO₂ formed by thermal oxidation areplotted. In FIGS. 2 and 3, the dependence of the flat band voltage Vfbof the hafnium silicate. (HfSiO) film on a film thickness is small, anda difference with the flat band voltage Vfb of the SiO₂ film shows thata fixed charge exists in the vicinity of the polycrystalline silicongate electrode of the hafnium silicate film. It can be understood that,when B (boron) is doped in the polycrystalline silicon gate electrode(FIG. 2), the flat band voltages Vfb of the hafnium silicate film areshifted in the negative direction about 0.6 to 0.7 V with respect to theflat band voltage Vfb of the SiO₂ film, and a positive fixed charge isgenerated. It can be understood that, when P (phosphorus) is doped inand As (arsenic) is doped in the gate electrode (FIG. 3), the flat bandvoltages Vfb of the hafnium silicate (Hf-silicate) are shifted in thepositive direction about 0.2 to 0.3 V with respect to the flat bandvoltages Vfb of the SiO₂ film, and a negative fixed charge is generated.

Note that, when the high dielectric constant film 104 is formed by usingonly TEOS, i.e., when a composition ratio of Hf is Hf/(Hf+Si)=0%, a flatband voltage Vfb was not generated. Further, when the gate electrode 106is formed from SiO_(0.8)Ge_(0.2) as well, the flat band voltage Vfbshows the trend in the same way as FIGS. 2 and 3. Accordingly, inaccordance with the results therefrom, it can be understood that a fixedcharge is generated when there, are Hf, Si, and a dopant.

In order to prevent B, P, As, or the like from being diffused to thesemiconductor substrate, a thin film, for example, an SiON film of about0.6 nm may be formed in advance on the semiconductor substrate beforethe gate insulating film is formed. This is because B, P, As or the likeis prevented from being diffused up to the semiconductor substrate atthe time of heat treatment in the process of manufacturing an LSI.

As described above, in the present embodiment, an anti-reaction filmformed from a silicon oxide film is provided between a silicate basedgate insulating film including hafnium and a polycrystalline silicongate electrode. Therefore, it is possible to suppress a fixed charge.

Second Embodiment

FIG. 4 is a second embodiment of the present invention, and in thisembodiment, an example in which the MOS structure is applied to acapacitor will be described.

The high dielectric constant film 104 such as a hafnium silicate isformed on a predetermined region of the silicon semiconductor substrate101, and the anti-reaction film 105 such as SiO₂ is formed on the highdielectric constant film 104. The high dielectric constant film 104 andthe anti-reaction film 105 constitute a dielectric substance film. Thepolycrystalline silicon electrode 106 is formed on the anti-reactionfilm 105. In accordance with such a constitution, a capacitor of the MOSstructure is composed of one side electrode including the siliconsemiconductor substrate 101, the dielectric substance film including thehigh dielectric constant film 104 and the anti-reaction film 105, andthe other side electrode including the polycrystalline silicon electrode106, and the same effect as in the transistor having the MOS structuredescribed in the first embodiment can be obtained. Further, variousmodifications are possible in the same way as in the transistor havingthe MOS structure described in the first embodiment.

Third Embodiment

Next, a third embodiment of the present invention will be described withreference to FIGS. 5 to 11.

FIGS. 5 to 11 are sectional views in respective processes ofmanufacturing a semiconductor apparatus according to the thirdembodiment of the present invention.

In this embodiment, processes of manufacturing an nMOS transistor willbe described. However, a pMOS transistor as well is formed on the samesilicon semiconductor substrate in the same processes. Namely, thepresent embodiment can be applied to a CMOS semiconductor apparatus.Moreover, this embodiment can be applied to a MOSFET of an SOI substrateas well, and can be also applied to a vertical MOS transistor (there isa channel in the vertical direction on the substrate, and electrons andholes run along it vertically with respect to the substrate).

First, as shown in FIG. 5, isolation regions 202 are formed by burying aSiO₂ film into trenches for isolation of a p-type silicon semiconductorsubstrate 201. Thereafter, a resist pattern, in which only the isolationregion divided by the isolation regions 202 is opened, is formed by aphotolithography method on the semiconductor substrate 201, and ann-type channel region 203 a is formed by injecting a dopant, forexample, B (boron) into the semiconductor substrate 201 from the openingportion by using the resist pattern as a mask. For example, the n-typechannel region 203 a is formed ion-implanting B (boron) into thesemiconductor substrate 201 at an accelerating voltage of 20 keV and adopant dose of 1×10₁₃ cm⁻³, and next, activating As (arsenic) byannealing for twenty minutes at 1000° C. in an N₂ atmosphere.

Next, as shown in FIG. 6, a hafnium silicate film 204 is formed so as tobe about 4 nm as a gate insulating film. Namely, the hafnium silicatefilm 204 in which a composition ratio of Hf is Hf/(Hf+Si)=30% isaccumulated to be formed by simultaneously supplying TEOS (Si(OC₂H₅)₄),HTB (Hf(OC(CH₃)₃)₄), and O₂ at 1 Torr and 600° C. by a CVD method.Subsequently, SiO₂ is formed so as to be about 1 nm as an anti-reactionfilm 205. The anti-reaction film 205 is accumulated to be formed bysimultaneously supplying TEOS (Si(OC₂H₅)₄) at 1 Torr and 600° C. by aCVD method.

Next, as shown in FIG. 7, a polycrystalline silicon film which will be agate electrode 206 a is accumulated so as to be 100 nm at 620° C. byusing a mixed gas of SiH₄, N₂, and H₂. Subsequently, a gate electrodeportion of the polycrystalline silicon film is covered with a resistpattern 207 by a photolithography method.

Next, as shown in FIG. 8, by using the photoresist 207 as a mask, a gateelectrode 206 a is formed by processing the polycrystalline silicon filmby RIE (Reactive Ion Etching) in a CF₄ and O₂ atmosphere. Thereafter, byusing the gate electrode 206 a as a mask, the anti-reaction film (SiO₂)205 and the high dielectric constant film 204 formed from hafniumsilicate are processed by using a solution containing HF. When the highdielectric constant film is formed from HfSiON, it is appropriate thatthe anti-reaction film and the composition ratio of N isN/(Hf+Si+O+N)=10 to 20 atom % around.

Next, as shown in FIG. 9, a silicon oxide (SiO₂) film is accumulated onan entire surface of the substrate 201, and then, gate side wallinsulating films 208 formed from a silicon oxide film are formed so asto have a thickness of about 5 nm by carrying out RIE etch-back.Subsequently, by using the gate electrode 206 a and the side wallinsulating films 208 as masks, As is ion-implanted into thesemiconductor substrate 201 at an accelerating voltage of 20 keV and adopant dose of 1×10¹⁵ cm⁻². Then, the gate electrode 206 b formed fromn-type silicon and source/drain regions 203 b and 203 c formed fromn-type silicon are formed due to the As (arsenic) being activated bycarrying out rapid thermal annealing (RTA) for ten seconds at 1000° C.

Next, after Co (cobalt) is accumulated on the entire surface of thesubstrate 201, heat treatment is carried out thereon, and thereafter,the residual Co is peeled off, whereby, as shown in FIG. 10, cobaltsilicide (CoSi₂) films 209 are formed on the gate electrode 206 b andthe source/drain regions 203 b and 203 c.

Next, as shown in FIG. 11, for example, an interlayer insulating film210 formed from SiO₂ is accumulate on the entire surface of thesubstrate 201 by using TEOS as a material, and then, the interlayerinsulating film 210 is flattened by chemical mechanical polishing (CMP).Subsequently, contact holes are formed so as to contact the source/drainregions 203 b and 203 c, and wiring films 211 formed from A1/TiN/Ti,Cu/TlN/Ti, or the like are formed in the contact holes and on theflattened interlayer insulating film 210. The wiring portions of thewiring films 211 in the contact holes electrically connect the wiringportions of the wiring films 211 on the interlayer insulating film 210and the source/drain regions 203 b and 203 c. Next, the semiconductorapparatus is completed by carrying out wiring processes from the secondlayer on.

As described above, in the present embodiment, an anti-reaction filmformed from a silicon oxide film is provided between a silicate basedgate insulating film including hafnium and a polycrystalline silicongate electrode. Therefore, it is possible to suppress a fixed charge.

Although not illustrated, a p-channel transistor which is complementaryto the n-channel MOS transistor as well is formed on the semiconductorsubstrate 201, and as shown in FIG. 12, complementary MOS (CMOS)transistors are constituted. The p-channel transistor is formed in thesame way as the n-channel transistor in a p-type well (not shown) formedat the semiconductor substrate 201.

Fourth Embodiment

Next, a fourth embodiment of the present invention will be describedwith reference to FIGS. 13 to 16.

FIGS. 13 to 16 are sectional views in respective processes ofmanufacturing a semiconductor apparatus according to the fourthembodiment of the present invention.

In this embodiment, processes of manufacturing an nMOS transistor willbe described. However, a pMOS transistor as well is formed on the samesilicon semiconductor substrate in the same processes. Namely, thepresent embodiment can be applied to a CMOS semiconductor apparatus.Moreover, this embodiment can be applied to a MOSFET of an 501 substrateas well, and can be also applied to a vertical MOS transistor.

First, as shown in FIG. 13, isolation regions 302 are formed by buryingan SiO₂ film into trenches for isolation of a p-type siliconsemiconductor substrate 301. Thereafter, a resist pattern, in which onlyisolation region divided by the isolation regions 302 is opened, isformed on the semiconductor substrate 301 by a photolithography method,and an n-type channel region 303 a is formed due to a dopant, forexample, As (arsenic) being injected into the semiconductor substrate301 from the opening portion by using the resist pattern as a mask. Forexample, the n-type channel region 303 a is formed by ion-implanting As(arsenic) into the semiconductor substrate 301 at an acceleratingvoltage of 20 keV and a dopant dose of 1×10¹³ cm⁻³, and next, activating3 by annealing for twenty minutes at 1000° C. in an N₂ atmosphere.

Next, as shown in FIG. 14, a high dielectric constant film 304 is formedso as to be about 5 nm by a film-forming method which is the same as thefilm-forming method of the high dielectric constant film 204 in thethird embodiment. Next, the surface layer of the high dielectricconstant film 304 is processed by using a mixed aqueous solution ofH₂SO₄/H₂O₂, and Hf in the surface layer is dissolved and extracted. As aresult, an anti-reaction film (SiO₂) 305 is formed on the layer portionwhere Hf has been extracted (FIG. 15). Hereinafter, by executingaccumulation of a polycrystalline silicon film, forming of a gateelectrode 306 b, injection of a dopant and activation of thesource/drain regions 303 b, 303 c, wiring processes, and the like by thesame methods as in the third embodiment, the semiconductor apparatus iscompleted as shown in FIG. 16. In FIG. 16, reference numeral 308 denotesa gate side wall insulating film, and corresponds to the gate side wallinsulating film 208 of FIG. 11 in the third embodiment. Referencenumeral 309 denotes a cobalt suicide (CoSi₂) film, and corresponds tothe cobalt silicide (CoSi₂) film 209 of FIG. 11. Reference numeral 311denotes a wiring, and corresponds to the wiring film 211 of FIG. 11.

As described above, in the present embodiment, an anti-reaction filmformed from a silicon oxide film is provided between a silicate basedgate insulating film including hafnium and a polycrystalline silicongate electrode. Therefore, it is possible to suppress a fixed charge.Also, in this embodiment, since the anti-reaction film is formed due toHf in the surface layer being dissolved and extracted by processing thesurface layer of the high dielectric constant film, it is easy tomanufacture the semiconductor apparatus. Further, various modificationsare possible in the same way as in the semiconductor device described inthe third embodiment.

Although not illustrated, a p-channel transistor which is complementaryto the n-channel MOS transistor as well is formed on the semiconductorsubstrate 301, and as shown in FIG. 12, complementary MOS (CMOS)transistors are constituted. The p-channel transistor is formed in thesame way as the n-channel transistor in a p-type well (not shown) formedat the semiconductor substrate 201.

Fifth Embodiment

Next, a fifth embodiment of the present invention will be described withreference to FIG. 17.

FIG. 17 is a sectional view in a process of manufacturing asemiconductor apparatus according to the fifth embodiment.

A method of forming an isolation region 402, a channel region 403 a, anda high dielectric constant film (hafnium silicate film) 404 on a siliconsemiconductor substrate 401 is the same as, for example, in the thirdembodiment. The high dielectric constant film may be, for example,HfSiON or the like in addition to HfSiO.

(1) As a raw material of silicon of a SiO₂ film which is ananti-reaction film 405 formed by using a CVD method, organic based,halogen based, and hydride based materials in addition to TEOS can beused. Examples of the organic based material include BTBAS(SiN₂(N(C(CH₃)₃)₂)) and TDMAS (Si(N(CH₃)₃)₂)), examples of the halogenbased material include SiH₂, C1₂, SiC1₄, Si₂C1₆, and SiF₄, and examplesof the hydride based material include SiH₄ and the like. Further, as agas, a single or a mixed gas which is selected from O₂, N₂O, and thelike is used in accordance with a material, a film-forming temperature,or the like.

(2) The SiO₂ film 405 may be formed by an ALD method using TEOS and H₂O.In place of TEOS, as described in the above-described (1), organicbased, halogen based, and hydride based materials may be used. Examplesof the organic based material include BTBAS (SiH₂(N(C(CH₃)₃)₂)) andTDMAS (Si(N(CN₃)₃)₂)), examples of the halogen based material includesSiH₂, C1₂, SiC1₄, Si2C1₆, and SiF₄, and examples of the hydride basedmaterial, SiH₄ and the like. O₂, O₃, H₂O₂, N₂O, or the like may be usedin place of H₂O.

(3) The SiO₂ film 405 may be formed such that by using SiH₄, and an Sifilm is formed in an H₂/N₂ atmosphere, and next, the Si film isoxidized. As a method of oxidizing the Si film, for example, annealingis carried out for 30 seconds at 800° C. and 1 Torr in an O₂ atmosphere.Or, the Si film may be oxidized by plasma oxidation in an Ar/O₂atmosphere. Or, the Si film may be oxidized by being immersed in anaqueous solution such as H₂SO₄, H₂O₂, or HNO₃, or a mixed solutionthereof. Or, the Si film may be oxidized by an anodic oxidation method.

(4) With respect to the SiO₂ film 405, the anti-reaction film (SiO₂film) 405 may be formed such that an SiN film is formed in an NH₃/N₂atmosphere by using SiH₄ as a raw material of Si, and next, the SiN filmis oxidized. As a method of oxidizing the SiN film, for example, themethod described in the above-described (3) can be used in which theannealing is carried out for 30 seconds at 800° C. and 1 Torr in an O₂atmosphere. At that time, some of N in the SiN film diffuse into thehafnium silicate film 404, and therefore, the additional effect that therelative dielectric constant is increased can be expected. Further, thematerials described in the above-described (1) may be used as a rawmaterial of Si. In that case, as a gas, a single or a mixed gas which isselected from NH₃, N₂H₄, H₂, N₂, N₂O, and the like is used in accordancewith a material, a film-forming temperature, or the like.

(5) The SiO₂ film 405 may be formed by a reactive sputtering method inan Ar/O₂ atmosphere by using an Si target. The Si is made to be theanti-reaction film 405 by being oxidized in an Ar/O₂ atmosphere. Notethat, at that time, the Si target is not necessarily provided directlyabove the Si substrate surface, but may be provided at a position out ofthe position directly above the Si substrate surface. Namely, theanti-reaction film 405 may be formed by a so-called off-axis method. Byusing the off-axis method, the effect that a damage to a hafniumsilicate film 404 by plasma at the time of forming film is reduced canbe obtained.

(6) The SiO₂ film 405 can be formed by a sputtering method in an Ar/O₂atmosphere by using an SiO₂ target.

(7) The SiO₂ film 405 can be formed by a reactive sputtering method inan Ar/N₂ atmosphere by using an Si target. Namely, the Si is made to bean SiN film by being nitrified in an Ar/N₂ atmosphere, and next, theSiO₂ film 405 is formed by oxidizing the SiN film. As an oxidizingmethod, the method described in the above-described (3) may be used.Formation of the SiO₂ film 405 may be carried out by combining themethod of (7) and the method of the above-described (6). For example,the anti-reaction film (SiO₂ film) 405 is formed such that an SiON filmis firmed by a reactive sputtering method in an Ar/N2/O₂ atmosphere byusing an SiO₂ target, and next, the SiON film is oxidized by the methoddescribed in the above-described (3).

As described above, in the present embodiment, an anti-reaction filmformed from a silicon oxide film is provided between a silicate basedgate insulating film including hafnium and a polycrystalline silicongate electrode.

Sixth Embodiment

Next, a sixth embodiment of the present invention will be described withreference to FIGS. 18 to 20.

FIG. 18 is a sectional view of a part of a semiconductor apparatus whichwill be described in this embodiment, and FIGS. 19 and 20 arerespectively sectional Views for explanation of a composition ratio ofan insulating film used for the semiconductor apparatus.

As a high dielectric substance gate insulating film in place of the SiO₂gate insulating film, HfSioN which is a high dielectric constant filmhas been thought to be promising. However, a shift in a flat bandvoltage Vfb of the HfSiON gate insulating film is large in a MOStransistor, in particular, in a p-MOS transistor (>0.4V). The fixedcharge causing the shift in Nfb is generated due to a dopant and Hf, andis mainly localized at the interface of poly-Si (polycrystallinesilicon) and HfSiON.

As shown in FIG. 18, in the semiconductor apparatus of the presentembodiment, an HfSiON film which is a high dielectric constant film isformed on a silicon substrate, an Hf_(x)Si_(1-x)O₂ film which is ananti-reaction film whose Hf density is lower (including x=0) than the Hfdensity of an HfSiON film is formed on the HfSiON film, and a poly-Siwhich is a gate electrode is formed on the Hf_(x)Si_(1-x)O₂ film. Next,a dopant is contained in the gate electrode, and then, the containeddopant is activated. Due to the dopant being contained in the gateelectrode and the contained dopant being activated, generation of afixed charge at the interface of the polycrystalline silicon gateelectrode and the HfSiON which is caused by the dopant can besuppressed.

In the present embodiment, HfSiON is used as a high dielectric constantfilm. The Hf density of the Hf_(x)Si_(1-x)O₂ film which is ananti-reaction film is low, and the Hf density is preferably less than orequal to 10¹³ cm⁻² in order to suppress generation of a fixed charge.Further, the film thickness of the Hf_(x)Si_(1-x)O₂ film is required tobe greater than or equal to 0.3 nit in order to maintain the effect.Furthermore, with respect to HfSiON, it is preferable that thecomposition ratio of Hf is Hf/(Hf+Si)=30 atom %, and the compositionratio of N is N/(Hf+Si+O+N)=10 to 20 atom % around. Zr may be used inplace of Hf.

Note that, in the insulating film formed from the Hf_(x)Si_(1-x)O₂ filmand the HfSiON film, the Hf density thereof may have a distribution inthe depth direction. For example, as in FIG. 20, the Hf density at theinterface side of the polycrystalline silicon gate electrode maybe madelow, and may be made high at the central portion thereof. However, asshown in FIG. 19, when Hf greater than or equal to 1 atom % exists atthe interface side of the polycrystalline silicon gate electrode, ashift in a flat band voltage Vfb is brought about. Accordingly, as shownin FIG. 20, SiO₂ must exist at the interface side of the polycrystallinesilicon gate electrode in order to suppress occurrence of a shift in aflat band voltage Vfb. SiO₂ has a function of suppressing a shift in aVfb.

As described above, in the present embodiment, an anti-reaction filmformed from an Hf_(x)Si_(1-x)O₂ film is provided between an HfSiON gateinsulating film and a polycrystalline silicon gate electrode containinga dopant.

In the embodiments as described above, the high dielectric constant filmis described as being made of an SiO₂ film containing Hf. However, thehigh dielectric constant film may be made of a film made of a materialcontaining at least one of Hf and Zr, and Si and O, or a film made of amaterial containing at least one of Hf and Zr, and Si, O and N. Further,the high dielectric constant film may be made of a material selectedfrom the group including HfSiO, HfSION, HfZrSiO, HfZrSiON, ZrSiO andZrSiON.

In the embodiments as described, the anti-reaction film provided betweenthe high dielectric constant gate insulation film and the silicon gateelectrode comprises an SiO₂ film. However, the high dielectric constantfilm is made of a film made of a material containing SiO₂ as a maincomponent and at least one of Hf and Zr, a film made of a materialcontaining SiO₂ as a main component, Hf and N, a film made of a materialcontaining SiO₂ as a main component, Zr and N, or a film made of amaterial

containing SiO₂ as a main component, Hf, Zr and N. The material of theanti-reaction film may be one selected from the group including HfSiO,HfSiON, HfZrSiO, HfZrSiON, ZrSiO and ZrSiON.

With these embodiments, it is possible to suppress a fixed chargegenerated between the high dielectric constant gate insulation film andthe silicon gate electrode. The high dielectric constant film maycontain A1, La, Ti, Ta, or Y, other than Hf and Zr.

It is preferable that, when the high dielectric constant film. containsone of Hf and Zr, (Hf or Zr)/C(Hf or Zr)+Si)=about 10 to 90 atom %, and(N/(Hf or Zr)+Si+O+N))=about. 10 to 20 atom %. Also, it is preferablethat, when the high dielectric constant film contains Hf and Zr, (Hf andZr)/((Hf and Zr)+Si)=about 10 to 90 atom %, and (N/(Hf andZr)−i−Si+O+N))=about 10 to 20 atom %.

When the anti-reaction film contains one of Hf and Zr, a compositionratio of Hf or Zr is less than 1 atom %, when the anti-reaction filmcontains Hf and Zr, a total composition ratio of Hf and Zr is less than1 atom %, and when the anti-reaction film contains N, a compositionratio of N is less than 20 atom %.

Further, the transistors having the gate insulation film structuresdescribed in the second to sixth embodiments can be applied totransistors of peripheral circuits such as sense amplifier circuits of anon-volatile memory apparatus, for example, a NAND type flash memory(electrically erasable non-volatile memory). The transistors having thegate insulation film structures described in the second to sixthembodiments can be applied to the transistors forming the senseamplifier circuit.

FIG. 21 shows a diagram of a NAND region 501 and a sense amplifiercircuit 502 as a peripheral circuit. The transistors having the gateinsulation film structures described in the second to sixth embodimentscan be applied to the transistors forming the sense amplifier circuit502.

FIG. 22 is a plan view showing the construction of a NAND type flashmemory. FIG. 23 is an equivalent circuit diagram of the constructionshown in FIG. 22.

As shown in FIGS. 22 and 23, each NAND cell unit is constructed suchthat memory cells M1 to M8 which are connected in series are arrangedbetween select transistors Si and S2. Select gate lines SG1 and SG2 areconnected to the select transistors S1 and S2, respectively, and controlgate lines (word lines) CG1 to CG8 are connected to the memory cells M1to M8, respectively. Also, bit lines (BL1, BL2, etc.) are connected tothe select transistor S1.

FIG. 24 a schematic diagram of a DRAM mixed LSI device or a SRAM mixedLSI device. The memory device comprises a memory cell array 601, a senseamplifier (S/A) circuit 602, a CPU (Central processing unit) 603, anaddress buffer 604, a row decoder 605, a column decoder 606, and an I/O(Input/output) buffer 607. The transistors having the gate insulationfilm structures described in the second to sixth embodiments can beapplied to the transistors of the peripheral circuits of the memorydevice, that is, the sense amplifier circuit 602, the address buffer604, the row decoder 605, the column decoder 606, the I/O buffer 607,and the like.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A semiconductor apparatus comprising: a semiconductor substrate; ahigh dielectric constant film formed over the semiconductor substrate,the high dielectric constant film comprising a film containing at leastone of hafnium (Hf) and zirconium (Zr), and silicon (Si), oxygen (O),and nitrogen (N); and an anti-reaction film formed on the highdielectric constant film, a thickness of the anti-reaction film beingthinner than a thickness of the high dielectric constant film, theanti-reaction film comprising a film selected from the group consistingof: a film containing Si, O, and Hf, where an amount of Hf containedtherein is less than in the high dielectric constant film, a filmcontaining Si, O, and Zr, where an amount of Zr contained therein isless than in the high dielectric constant film, a film containing Si, O,Hf, and Zr, where an amount of Hf and Zr contained therein is less thanin the high dielectric constant film, a film containing Si, O, and N, afilm containing Si, O, N, and Hf, where an amount of Hf containedtherein is less than in the high dielectric constant film, a filmcontaining Si, O, N, and Zr, where an amount of Zr contained therein isless than in the high dielectric constant film, and a film containingSi, O, N, Hf, and Zr, where an amount of Hf and Zr contained therein isless than in the high dielectric constant film; and a gate electrodeformed on the anti-reaction film, the gate electrode containing Si andadded with dopant.
 2. The semiconductor apparatus according to claim 1,wherein the high dielectric constant film is made of a material selectedfrom the group including hafnium silicon oxynitride (HfSiON), hafniumzirconium silicon oxynitride (HfZrSiON), and zirconium siliconoxynitride (ZrSiON).
 3. The semiconductor apparatus according to claim1, wherein, when the high dielectric constant film contains one of Hfand Zr, (Hf or Zr)/((Hf or Zr) +Si)=about 10 to 90 atom %, and (N/(Hf orZr)+Si+O+N)=about 10 to 20 atom %.
 4. The semiconductor apparatusaccording to claim 1, wherein, when the high dielectric constant filmcontains Hf and Zr, (Hf and Zr)/((Hf and Zr)+Si)=about 10 to 90 atom %,and (N/(Hf and Zr)+Si+O+N))=about 10 to 20 atom %.
 5. The semiconductorapparatus according to claim 1, wherein the anti-reaction film is oneselected from the group including: a film containing Si, O, and at leastone of Hf and Zr, a film containing Si, O, Hf, and N, a film containingSi, O, Zr, and N, and a film containing Si, O, Hf, Zr, and N, andwherein the material of the high dielectric constant film is oneselected from the group including hafnium silicon oxynitride (HfSiON),hafnium zirconium silicon oxynitride (HfZrSiON), and zirconium siliconoxynitride (ZrSiON).
 6. The semiconductor apparatus according to claim1, wherein the semiconductor substrate comprises a silicon substrate oran SOl substrate.
 7. The semiconductor apparatus according to claim 1,wherein the semiconductor substrate, the high dielectric constant film,the anti-reaction film, and the gate electrode constitute a transistoror a capacitor.
 8. The semiconductor apparatus according to claim 7,wherein the transistor comprises an n-type MOS transistor having ann-channel region.
 9. The semiconductor apparatus according to claim 7,wherein the transistor comprises a p-type MOS transistor having ap-channel region.
 10. The semiconductor apparatus according to claim 7,wherein the transistor comprises a complementary MOS transistor having ap-channel region and n-channel region.
 11. The semiconductor apparatusaccording to claim 1, wherein the gate electrode contains Si as a maincomponent and at least one of B, P, and As.
 12. The semiconductorapparatus according to claim 1, wherein the gate electrode comprisesSi_(1-x)Ge_(x)(0≦x≦0.8).
 13. The semiconductor apparatus according toclaim 1, wherein the gate electrode contains Si and a metal as a maincomponent, and the metal is one selected from the group of Fe, Co, Ni,Ti, Hf, Zr, and W.
 14. The semiconductor apparatus according to claim 1,wherein a thickness of the anti-reaction film in terms of SiO2 isthinner than a thickness of the high dielectric constant film in termsof SiO₂.
 15. A semiconductor apparatus comprising: a semiconductorsubstrate; a diffusion prevention film formed on the semiconductorsubstrate, the diffusion prevention film containing silicon (Si), oxygen(O), and nitrogen (N); a high dielectric constant film formed on thediffusion prevention film, the high dielectric constant film comprisinga film selected from the group consisting of: a film containing at leastone of hafnium (Hf) and zirconium (Zr), and silicon (Si) and oxygen (O),and a film containing at least one of Hf and Zr, and Si, O, and nitrogen(N); and an anti-reaction film formed on the high dielectric constantfilm, a thickness of the anti-reaction film being thinner than athickness of the high dielectric constant film, the anti-reaction filmcomprising a film selected from the group consisting of: a filmcontaining Si, O, and Hf, where an amount of Hf contained therein isless than in the high dielectric constant film, a film containing Si, O,and Zr, where an amount of Zr contained therein is less than in the highdielectric constant film, a film containing Si, O, Hf, and Zr, where anamount of Hf and Zr contained therein is less than in the highdielectric constant film, a film containing Si, O, and N, a filmcontaining Si, O, N, and Hf, where an amount of Hf contained therein isless than in the high dielectric constant film, a film containing Si, O,N, and Zr, where an amount of Zr contained therein is less than in thehigh dielectric constant film, and a film containing Si, O, N, Hf, andZr, where an amount of Hf and Zr contained therein is less than in thehigh dielectric constant film; and a gate electrode formed on theanti-reaction film, the gate electrode containing Si and added withdopant.
 16. The semiconductor apparatus according to claim 15, whereinthe high dielectric constant film is made of a material selected fromthe group including hafnium silicate (HfSiO), hafnium silicon oxynitride(HfSiON), hafnium zirconium silicate (HfZrSiO), hafnium zirconiumsilicon oxynitride (HfZrSiON), zirconium silicate (ZrSiO), and zirconiumsilicon oxynitride (ZrSiON).
 17. The semiconductor apparatus accordingto claim 15, wherein a thickness of the anti-reaction film in terms ofSiO2 is thinner than a thickness of the high dielectric constant film interms of SiO2.
 18. A semiconductor apparatus comprising: a semiconductorsubstrate; a diffusion prevention film formed on the semiconductorsubstrate, the diffusion prevention film containing silicon (Si), oxygen(O), and nitrogen (N); a high dielectric constant film formed on thediffusion prevention film, the high dielectric constant film comprisinga film selected from the group consisting of: a film containing at leastone of hafnium (Hf) and zirconium (Zr), and silicon (Si) and oxygen (O),and a film containing at least one of Hf and Zr, and Si, O, and nitrogen(N); and an anti-reaction film formed on the high dielectric constantfilm, the anti-reaction film comprising a film selected from the groupconsisting of: a film containing Si, O, and N, a film containing Si, O,N, and Hf, where an amount of Hf contained therein is less than in thehigh dielectric constant film, a film containing Si, O, N, and Zr, wherean amount of Zr contained therein is less than in the high dielectricconstant film, and a film containing Si, O, N, Hf, and Zr, where anamount of Hf and Zr contained therein is less than in the highdielectric constant film; and a gate electrode formed on theanti-reaction film, the gate electrode containing Si and added withdopant.
 19. The semiconductor apparatus according to claim 18, whereinthe high dielectric constant film is made of a material selected fromthe group including hafnium silicate (HfSiO), hafnium silicon oxynitride(HfSiON), hafnium zirconium silicate (HfZrSiO), hafnium zirconiumsilicon oxynitride (HfZrSiON), zirconium silicate (ZrSiO), and zirconiumsilicon oxynitride (ZrSiON).
 20. The semiconductor apparatus accordingto claim 18, wherein a thickness of the anti-reaction film in terms ofSiO₂ is thinner than a thickness of the high dielectric constant film interms of SiO₂.